Fail to build out of the box on Mac OS X

I have tried to build on Mac OS X and had to do the following fixes to make it pass:

diff --git a/cmake/FindGRPC.cmake b/cmake/FindGRPC.cmake
index df19edd..8c65838 100644
--- a/cmake/FindGRPC.cmake
+++ b/cmake/FindGRPC.cmake
@@ -77,7 +77,7 @@ endfunction()


 set(protobuf_MODULE_COMPATIBLE TRUE)
-  find_package(Protobuf CONFIG REQUIRED)
+  find_package(Protobuf REQUIRED)
   message(STATUS "Using protobuf ${Protobuf_VERSION}")

   set(PROTOBUF_LIBPROTOBUF protobuf::libprotobuf)

-> there is no Protobuf.Config.cmake file to be found

diff --git a/lib/tethys/tethys_graph.cpp b/lib/tethys/tethys_graph.cpp
index 1fee707..219e5bd 100644
--- a/lib/tethys/tethys_graph.cpp
+++ b/lib/tethys/tethys_graph.cpp
@@ -534,7 +534,7 @@ size_t TethysGraph::get_flow() const
     }

     size_t flow = 0;
-    for (const EdgePtr e_ptr : source.out_edges) {
+    for (const EdgePtr &e_ptr : source.out_edges) {
         // cppcheck-suppress useStlAlgorithm
         flow += edges[e_ptr].flow;
     }

The c++ compiler chokes on the lack of reference operator.